1. Field of the Invention
The invention relates to a forward looking radar for two-dimensional imaging of land or sea surfaces including objects detectable there in a forward lying sector region of flying or stationary carriers.
2. Description of the Prior Art
In present-day airborn imaging radar systems there is a system-inherent gap in the nadir region because with such systems the overflown terrain or sea can be picked up only to the right and left of the flight path. For a gapless radar imaging of the overflown area however, a sensor is required which with comparable resolution fills out the hitherto missing portion.
In many measuring tasks, for example in measuring marine polution, various sensors would have to be combined with each other. With down looking sensors, for example radiometers, IR scanners and the like, an aircraft must frequently be exactly guided over an area even with noground visibility. For this purpose however an imaging radar device is required which is installed in the aircraft and can operate independently of any ground station because radio navigation, depending on the geographical location, is either too inaccurate or not possible at all.
At present no apparatuses are available for the problems outlined above. In flight operations however weather radar systems are used which operate with a socalled "ground mapping mode". These devices have a mechanically scanned antenna so that the geometric and radiometric resolution is system-inherently very low.
The detection gap in the nadir region referred to at the beginning cannot be filled with the existing systems either. Furthermore, the existing devices, because of their low resolution, cannot even be used as navigation aid. Operational use, for example use in aircraft, is not possible because of the mechanical pivoting of the antennas. Moreover, apart from the mechanical difficulties as regards weight, volume, radome and the like, the repetition rate is too low.